Overview
This lecture explores the origins of nutrients in our food, the role of plant and soil diversity in nutrient availability, and compares the impacts of monoculture and polyculture agricultural systems.
Disconnect from Food Production
- Only about 1.3% of the U.S. workforce works on farms; most people are disconnected from how food is produced.
- Lack of awareness about food sources leads to misunderstanding where nutrients in our food originate.
Sources of Nutrients in Food
- Animal products like steak derive nutrients (proteins, fats, vitamins, and minerals) that ultimately originate from plants.
- Plants obtain nutrients from the soil, which contains minerals like calcium, magnesium, iron, potassium, sodium, phosphate, and nitrate.
Soil-Plant-Microbe Interactions
- Soil nutrients are often bound to soil particles and not freely available to plants.
- Microorganisms (bacteria, fungi, protists) help release these nutrients by breaking them free from soil particles.
- Dead microorganisms decompose and make these nutrients bioavailable to plants.
- Plants use photosynthesis to make sugars, some of which are exuded from roots (root exudates) to feed soil microorganisms.
Importance of Plant and Insect Diversity
- Diverse plant species produce a variety of root exudates, attracting a diverse set of soil microorganisms.
- Greater soil microbe diversity leads to more nutrient-rich plants.
- Plant diversity also attracts beneficial insects (pollinators and predators), reducing the need for pesticides.
Monoculture vs. Polyculture Systems
- Monoculture (growing one crop species) leads to low plant, soil, and insect diversity.
- Low diversity results in nutrient-poor food, higher pest pressure (requiring more pesticides), and greater reliance on synthetic fertilizers.
- Synthetic fertilizers often run off into waterways, causing environmental harm (e.g., Gulf of Mexico dead zone).
- Food production is the main threat to about 86% of species threatened with extinction.
Benefits of Diverse Agricultural Systems
- Polyculture and diverse systems produce more nutritious food.
- High diversity of plants supports natural pest control and reduces pesticide use.
- Organic fertilizers recycle waste and reduce pollution, providing more nutrients to crops.
The Value of Growing Your Own Food
- Growing your own food is accessible, educational, and improves health and nutrition.
- Teaching children to garden helps them understand where food and nutrients come from.
Key Terms & Definitions
- Monoculture — The agricultural practice of growing a single crop species in a field each season.
- Polyculture — Growing multiple crop species in the same space to promote biodiversity.
- Root Exudates — Sugars and other compounds secreted by plant roots to feed soil microorganisms.
- Bioavailable Nutrients — Nutrients in a form that can be absorbed and used by living organisms.
- Synthetic Fertilizers — Man-made chemicals added to soil to increase nutrient content.
- Organic Fertilizers — Natural materials (food scraps, yard waste) used to enrich soil.
Action Items / Next Steps
- Research examples of successful polyculture or agroecological systems.
- If possible, try growing a simple crop or plant at home.
- Read about the environmental effects of fertilizer runoff, such as the Gulf of Mexico dead zone.